It is well accepted that synthetic microenvironments can be engineered to promote the formation of blood vessels within tissue-engineered constructs, but that these synthetic microenvironments do not result in stable vascular networks that are long lasting. This has been a particular problem with presentation of the most well characterized angiogenic growth factor, vascular endothelial growth factor (VEGF). Our long-term goal is to gain a molecular understanding of engineered vascular microenvironments and to use this information to better design scaffolds for therapeutic angiogenesis. Based on published and preliminary data we have found that the method of VEGF ligand presentation in tissue engineering scaffolds affects not only the physical stability and release kinetics of the growth factor, but also the molecular signals conveyed to the residing cells and ultimately the morphology and maturity of the resulting vascular network formed. In this proposal, we want to further investigate how VEGF ligand presentation affects VR-2 phosphorylation and the resulting cellular outcomes (phenotype and vessel morphology) in vitro and in vivo. Aim 1 and Aim 2 investigate how VEGF ligand presentation and synergistic signaling between VEGF and integrin ligands modulate activation of VEGF receptor-2 (VR-2), downstream signaling and endothelial cell branching. Aim 3 uses the knowledge gained from Aims 1 and 2 to design hydrogel scaffolds for revascularization of the brain after stroke. !